Laminate

ABSTRACT

The present invention provides a laminate used for a printed wiring substrate and a multilayer printed wiring board which have high heat resistance, wiring patterns with narrow pitches, vias with a small diameter, insulating layer having uniform thickness and stable adhesion between the metal layer and the synthetic resin film, and which contribute to miniaturization, high capability and functional improvement of electronic equipment. The present invention relates to a metal laminate comprising a metal layer laminated on one or both faces of a synthetic resin film, wherein the metal layer is a metal foil having a thickness of at most 5 μm. The present invention also relates to a laminate comprising a metal layer having a thickness of at most 5 μm on one or both faces of a synthetic resin film, wherein the synthetic resin film is a polyimide film obtained by immersing a partially imidized or partially dried poly(amide acid) film in a solution of a compound containing at least one element selected from the group consisting of aluminum, silicon, titanium, manganese, iron, cobalt, copper, zinc, tin, antimony, lead, bismuth and palladium or by applying the solution to the film, and then completely drying and imidizing the poly(amide acid) film, the resulting polyimide film containing at least one of the elements.

TECHNICAL FIELD

[0001] The present invention relates to a laminate comprising asynthetic resin film and a metal layer laminated on each other, and moreparticularly, a laminate which can provide a printed wiring substrateand a multilayer printed wiring board having high heat resistance,wiring patterns with narrow pitches, vias with a small diameter,insulating layer having uniform thickness and stable adhesion betweenthe metal layer and the synthetic resin film.

BACKGROUND ART

[0002] With the advancement of miniaturization, high capability andfunctional improvement of electronic equipment, wiring boards arerequired to be suitable for high density installation. In order tosatisfy such requirement, wiring boards are made multilayered, aninsulating layer is thinned, a via diameter is made small, and a circuitis made to have narrow pitches.

[0003] As the technology for achieving such advancement, to make a metallayer thin has been known effective and there have been proposed methodsfor obtaining circuit substrates with a thin metal layer by forming athin film of a metal on the synthetic resin film surface by vacuumevaporation or sputtering, and forming a metal layer with a prescribedthickness on the film by electroplating, and some of the methods areemployed practically. However, the methods have a problem that theadhesion strength of the film surface and the metal thin film is low orthat the heat resistance of the adhesion is low. Further, in order toavoid such a problem, there are methods comprising steps of forming, onthe surface of a synthetic resin film, a thin film of a metal, which isdifferent from a metal to form a circuit and has excellent adhesionproperty to a synthetic resin film, and then forming a metal with whicha circuit is formed. Even by such methods, not only sufficient adhesionstrength between the film surface and the metal layer cannot be obtainedbut also there occurs a problem in the electric resistance stability incircuits owing to the lamination of two or more kinds of metals.Further, there are other problems that the metal layers formed by acombination of thin film formation by vacuum evaporation, sputtering orthe like with a plating method have pin holes and uneven layerthickness.

[0004] On the other hand, in order to obtain a laminate with a thinmetal layer, it is supposed to be proper to use a thin metal foil.However, when the metal foil is thin, the metal foil ruptures owing tothe insufficient strength and causes a problem of wrinkling at the timeof lamination and therefore it is required for the metal foil to have athickness of at least 10 μm in order to stably manufacture the laminate.

[0005] The present invention aims to solve such problems and provide alaminate for a printed wiring substrate and a multilayer printed wiringboard which have high heat resistance, wiring patterns with narrowpitches, vias with a small diameter, insulating layer having uniformthickness and stable adhesion between the metal layer and the syntheticresin film, and which contribute to miniaturization, high capability andfunctional improvement of electronic equipment.

DISCLOSURE OF INVENTION

[0006] In order to solve the above described problems, enthusiasticinvestigations have been made and accordingly it has been found that alaminate having high heat resistance, wiring patterns with narrowpitches, vias with a small diameter, insulating layer having uniformthickness and stable adhesion between the metal layer and the syntheticresin film can be obtained by laminating a metal foil with a specifiedthickness and a synthetic resin film to achieve the present invention.Further, it has been found that a laminate having high heat resistance,wiring patterns with narrow pitches, vias with a small diameter,insulating layer having uniform thickness, and stable adhesion betweenthe metal layer and the synthetic resin film can be obtained bylaminating a metal layer and a polyimide film subjected to a specifiedsurface treatment to achieve the present invention.

[0007] That is, the present invention relates to a laminate comprising ametal layer laminated on one or both faces of a synthetic resin film,wherein the metal layer is a metal foil having a thickness of at most 5μm.

[0008] It is preferable that the metal layer is laminated on one face ofthe synthetic resin film and an adhesive layer is laminated on the otherface of the synthetic resin film.

[0009] It is preferable that the synthetic resin film and the metallayer are bonded with an adhesive.

[0010] It is preferable that the adhesive contains a polyimide resin.

[0011] It is preferable that the adhesive containing the polyimide resincontains a thermosetting resin.

[0012] It is preferable that the adhesive is laminated on a metal layeror a circuit substrate at a temperature of at most 220° C.

[0013] It is preferable that a polyimide film is used as the syntheticresin film.

[0014] It is preferable that the polyimide film has a thickness of atmost 50 μm, a tensile modulus of at least 4 GPa and a coefficient oflinear expansion of at most 20 ppm.

[0015] It is preferable that the metal foil is a metal foil supported bya carrier.

[0016] It is preferable that the synthetic resin film is a polyimidefilm obtained by immersing a partially imidized or partially driedpoly(amide acid) film in a solution of a compound containing at leastone element selected from the group consisting of aluminum, silicon,titanium, manganese, iron, cobalt, copper, zinc, tin, antimony, lead,bismuth and palladium or by applying the solution to the film, and thencompletely drying and imidizing the poly(amide acid) film, the resultingpolyimide film containing at least one of the elements.

[0017] The present invention also relates to a laminate comprising ametal layer having a thickness of at most 5 μm on one or both faces of asynthetic resin film, wherein the synthetic resin film is a polyimidefilm obtained by immersing a partially imidized or partially driedpoly(amide acid) film in a solution of a compound containing at leastone element selected from the group consisting of aluminum, silicon,titanium, manganese, iron, cobalt, copper, zinc, tin, antimony, lead,bismuth and palladium or by applying the solution to the film, and thencompletely drying and imidizing the poly(amide acid) film, the resultingpolyimide film containing at least one of the elements.

[0018] It is preferable that a metal layer having a thickness of at most5 μm is laminated on one face of the synthetic resin film and anadhesive layer is laminated on the other face of the synthetic resinfilm.

[0019] It is preferable that the adhesive contains a polyimide resin.

[0020] It is preferable that the adhesive contains a thermosettingresin.

[0021] It is preferable that the adhesive is laminated on a metal layeror a circuit substrate at a temperature of at most 220° C.

[0022] It is preferable that the metal layer is formed directly on thesynthetic resin film by a method selected from the group consisting ofsputtering, ion plating, electron beam evaporation, resistance heatingevaporation, chemical plating, and electroplating.

BEST MODE FOR CARRYING OUT THE INVENTION

[0023] The laminate of the present invention comprises a metal layer onone or both faces of a synthetic resin film. A wiring circuit is formedwith the metal layer of the laminate to give a printed wiring board.

[0024] The synthetic resin film which constitutes the laminate of thepresent invention is preferably a polyimide film in view of the highheat resistance, excellent electric insulation property and flexibility.

[0025] For the metal layer, a metal foil is used since stable bondingstrength can be obtained by metal foil surface roughening technique. Ametal of the metal foil includes metals such as copper (Cu), aluminum(Al), gold (Au), silver (Ag), chromium (Cr), nickel (Ni), tungsten (W),titanium (Ti), molybdenum (Mo) and cobalt (Co). The metal may be used asa single element or in form of alloy of two or more. Especially, as amaterial for a wiring circuit, copper and a copper alloy, which have alow electric resistance, are preferable.

[0026] The thickness of the metal foil is at most 5 μm, preferably atmost 3 μm. If thicker than 5 μm, formation of circuits with narrowpitches, which is a purpose of the present invention, becomes difficult.Incidentally, if the metal foil has a conductivity necessary to operatethe circuits, there is no lower limit of the thickness. However, in caseof the metal foil, the lower limit is about 0.5 μm on the basis of thepresent technical level from the viewpoint of the lower limit of thethickness to produce a metal foil which is sufficiently uniform foractual use, and of easy handling of the foil at the time of producingthe laminate. Above all, a copper foil with a thickness of at most 5 μmis preferable for forming wiring patterns with narrow pitches and viaswith a small diameter.

[0027] In the present invention, a metal foil such as a copper foil witha thickness of at most 5 μm can be laminated flatly with a high adhesionstrength to a synthetic resin film with no surface unevenness andexcellent appearance. According to this, further preferable wiringpatterns with narrow pitches and vias with a small diameter are madepossible to be formed.

[0028] The method for forming a metal foil on one or both faces of thesynthetic resin film includes a method for laminating a metal foil suchas a copper foil with an adhesive, a method by spreading and applying asynthetic resin solution on a metal foil and then drying, a method byspreading and applying a synthetic resin in melted state on a metal foiland then cooling and curing the resin, a method by setting athermoplastic resin sheet and a metal foil face to face and laminatingby pressurizing and/or heating them by a press or lamination method, anda method by setting a thermosetting resin sheet and a metal foil face toface and laminating by pressurizing and/or heating them by press orlamination method. Above all, it is preferable to laminate the metalfoil with an adhesive from the viewpoint of bonding strength andadhesion strength between the synthetic resin film and the metal foil;heat resistance and heat-and-moisture resistance of the adhesion;evenness of electric resistance of circuits; evenness of the thicknessof the metal foil; the number of defects such as pin holes; andproductivity of the laminate.

[0029] It is preferable that the laminate of the present inventioncomprises a metal layer on one face and an adhesive layer on the otherface of the synthetic resin film. The laminate with such a structure canbe suitably used for producing a so-called build-up type substratewherein an insulating layer and a metal layer are formed on the surfaceof a printed wiring board. In case of producing a multilayer wiringboard by using such a laminate according to the build-up method, it ispossible to prevent the insulating layer from becoming extremely thinand uniform thickness of the insulating layer can be achieved since thesynthetic resin film and the adhesive layer form an insulating layer.

[0030] The adhesive layer is laminated on the opposite face to the faceof the synthetic resin film where the metal layer is formed. Theadhesive which constitutes the adhesive layer includes those similar tothe adhesive used for bonding the synthetic resin film and the metalfilm.

[0031] The laminate of the present invention is laminated on an innerlayer board by heat press, roll heating or such method, and used as amultilayer board. In this case, the adhesive layer located on one faceof the laminate is brought into contact with a circuit of the innerlayer board and melted and bonded to the board. Accordingly, the innerlayer circuit is fixed while being buried in the adhesive. The surfaceroughness by the inner layer circuit can be smoothed by flow of theadhesive into the uneven surface of the inner layer circuit owing to thethermal fluidity of the adhesive at the time of laminating process.

[0032] A resin composition to be employed as the adhesive to bond thesynthetic resin film and metal foil, and as the adhesive whichconstitutes the adhesive layer is not particularly limited in the type,and a variety of well known resins can be employed. The types of theresins can be roughly classified into thermofusible adhesives usingthermoplastic resins and curable type adhesives based on the curingreaction of thermosetting resins. The thermoplastic resins include apolyimide resin, a poly(amide imide) resin, a poly(ether imide) resin, apolyamide resin, a polyester resin, a polycarbonate resin, apolyketoneresin, a polysulfone resin, a polyphenylene ether resin, apolyolefin resin, a polyphenylene sulfide resin, a fluoro resin, apolyallylate resin, a liquid crystal polymer resin and the like. Theymay be used alone or in combination of two or more for the adhesivelayer of the laminate of the present invention. Above all, it ispreferable to use a thermoplastic polyimide resin from the viewpoint ofexcellent heat resistance and electric reliability.

[0033] Herein, the method of producing a thermoplastic polyimide resinis described. The polyimide resin can be obtained from a solution of apoly(amide acid) polymer, which is a precursor of the polyimide. Thepoly(amide acid) polymer solution can be produced by a known method.That is, the solution can be obtained by polymerizing practically equalmole of a tetracarboxylic acid dianhydride component and a diaminecomponent in an organic polar solvent. The acid dianhydride to be usedfor the thermoplastic polyimide resin is not particularly limited aslong as it is an acid dianhydride. Examples of acid dianhydridecomponents include aliphatic or alicyclic tetracarboxylic aciddianhydrides such as butanetetracarboxylic acid dianhydride,1,2,3,4-cyclobutanetetracarboxylic acid dianhydride,1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride,1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,2,3,5-tricarboxycyclopentylacetate dianhydride,3,5,6-tricarboxynorbornane-2-acetic acid dianhydride,2,3,4,5-tetrahydrofurantetracarboxylic acid dianhydride,5-(2,5-dioxotetrahydrofuranyl)-3-methyl-3-cyclohexene-1,2-dicarboylicacid dianhydride, bicyclo[2,2,2]-oct-7-ene-2,3,5,6-tetracarboxylic aciddianhydride; aromatic tetracarboxylic acid dianhydrides such aspyromellitic acid dianhydride, 3,3′,4,4′-benzophenonetetracarboxylicacid dianhydride, 3,3′,4,4′-diphenylsulfonetetracarboxylic aciddianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride,2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 4,4′-oxyphthalicacid anhydride, 3,3′,4,4′-dimethyldiphenylsilanetetracarboxylic aciddianhydride, 3,3′,4,4′-tetraphenylsilanetetracarboxylic aciddianhydride, 1,2,3,4-furantetracarboxylic acid dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfide dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenylpropane dianhydride,4,4′-hexafluoroisopropylidenediphthalic acid anhydride,3,3′,4,4′-biphenyltetracarboxylic acid dianhydride,2,3,3′,4′-diphenyltetracarboxylic acid dianhydride, bis(phthalicacid)phenylsulfine oxide dianhydride, p-phenylene-bis(triphenylphthalicacid) dianhydride, m-phenylene-bis(triphenylphthalic acid) dianhydride,bis(triphenylphthalic acid)-4,4′-diphenyl ether dianhydride,bis(triphenylphthalic acid)-4,4′-diphenylmethane dianhydride; and2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3′,4,4′-tetracarboxylic aciddianhydride. In order to obtain excellent thermofusibility, it ispreferable to use2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3′,4,4′-tetracarboxylic aciddianhydride, 4,4′-hexafluoroisopropylidenediphthalic acid anhydride,2,3,3′,4′-biphenyltetracarboxylic acid dianhydride, 4,4′-oxydiphthalicacid anhydride and 3,3′,4,4′-benzophenonetetracarboxylic aciddianhydride.

[0034] Examples of diamine components include 4,4′-diaminodiphenylether, 3,4′-diaminodiphenyl ether, 2,2-bis(4-aminophenoxyphenyl)propane,1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene,1,3-bis(3-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]sulfone, 4,4′-bis(4-aminophenoxy)biphenyl,2,2-bis(4-aminophenoxyphenyl)hexafluoropropane,4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone,9,9-bis(4-aminophenyl)fluorene, bisaminophenoxy ketone,4,4′-[1,4-phenylenebis(1-methylethylidene)]bisaniline,4,4′-[1,3-phenylenebis(1-methylethylidene)]bisaniline and the like. Theymay be used alone or in combination of two or more.

[0035] The organic polar solvent to be employed for the generationreaction of the poly(amide acid) solution include, for example,sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide;formamide solvents such as N,N-dimethylformamide andN,N-diethylformamide; acetamide solvents such as N,N-dimethylacetamideand N,N-diethylacetamide; pyrrolidone solvents such asN-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenol solvents suchas phenol, o-, m- or p-cresol, xylenol, halogenated phenol and catechol;hexamethyl phosphorus amide; γ-butyrolactone and the like. Further,based on the necessity, these organic polar solvents may be used incombination with an aromatic hydrocarbon such as xylene or toluene.

[0036] The thus-obtained poly(amide acid) polymer solution is subjectedto dehydration ring closing by a thermal or chemical method to obtain athermoplastic polyimide resin. Both of the thermal method of dehydratingthe poly(amide acid) solution by heating and the chemical method ofdehydrating the poly(amide acid) solution using a dehydration agent canbe employed.

[0037] Examples of methods of the thermal dehydration ring closinginclude a method such that an imidization reaction of the poly(amideacid) solution is promoted by heating while evaporating a solventsimultaneously. According to this method, a solid thermoplasticpolyimide resin can be obtained. The heating conditions are notparticularly limited, but it is preferable to carry out the heating at atemperature of 200° C. or lower for about 5 to 120 minutes.

[0038] Examples of methods of the chemical dehydration ring closinginclude a method such that dehydration reaction is carried out byadding, to the poly(amide acid) solution, a catalyst and a dehydratingagent in an amount equal to or more than the stoichiometric amount, andby evaporating the organic solvent. Accordingly, a solid thermoplasticpolyimide resin can be obtained. The dehydrating agent for the chemicalmethod includes, for example, aliphatic acid anhydrides such as aceticacid anhydride and aromatic acid anhydrides such as benzoic acidanhydride. Examples of catalyst include aliphatic tertiary amines suchas triethylamine; aromatic tertiary amines such as dimethylaniline; andheterocyclic tertiary amines such as pyridine, α-picoline, β-picoline,γ-picoline and isoquinoline. Preferably, the chemical dehydration ringclosing is carried out at temperature of 100° C. or lower, and theevaporation of the organic solvent is carried out at a temperature of200° C. or lower for about 5 to 120 minutes.

[0039] As another method for obtaining a thermoplastic polyimide resin,there is a method such that solvent evaporation is not carried out inthe above thermal or chemical dehydration ring closing. To say moreparticularly, it is a method for obtaining a solid polyimide resin,which comprises adding, to a poor solvent, a polyimide resin solutionobtained by thermal imidization treatment or chemical imidizationtreatment by using a dehydration agent to precipitate the polyimideresin, removing unreacted monomers, and refining and drying theresulting resin. As the poor solvent, one which mixes well with asolvent but to which the polyimide is not easily dissolved should beselected. Examples include acetone, methanol, ethanol, isopropanol,benzene, methyl cellosolve, methyl ethyl ketone and the like, but thepoor solvent is not limited to these examples. The thermoplasticpolyimide resin can be obtained by these methods and used as theadhesive layer of the laminate of the present invention.

[0040] Further, as the adhesive, there is a curing adhesive using thecuring reaction of a thermosetting resin. Examples of such thermosettingresin include a bismaleimide resin, a bisallylnadiimide resin, a phenolresin, a cyanate resin, an epoxy resin, an acrylic resin, a methacrylicresin, a triazine resin, a hydrosilyl curing resin, an allyl curingresin, an unsaturated polyester resin, a thermosetting polyimide resinand the like. They may be used alone or in combination. Other than theabove thermosetting resins, thermosetting polymers containing a reactivegroup in side chains can also be used as the thermosetting component.The thermosetting polymers containing a reactive group in side chainsare those which have a reactive group such as an epoxy group, an allylgroup, a vinyl group, an alkoxysilyl group or a hydrosilyl group in theside chains or terminals of polymer chains. Among these, thermosettingpolyimide resins containing a reactive group in the polyimide skeletonare excellent in heat resistance and preferable for the adhesive layerof the present invention.

[0041] The thermosetting polyimide resin containing a reactive group inside chains is described below. As an example of a practical productionmethod, there are (1) a method for obtaining a thermosetting polyimidein accordance with the method of producing a thermoplastic polyimideresin mentioned above, in which diamine components and acid dianhydridecomponents having a functional group such as an epoxy group, a vinylgroup, an allyl group, a methacryl group, an acryl group, an alkoxysilylgroup, a hydrosilyl group, a carboxy group, a hydroxy group and a cyanogroup are used as the monomer components and (2) a method of obtaining athermosetting polyimide resin by producing a solvent-soluble polyimidehaving a hydroxyl group, a carboxyl group or an aromatic halogen groupaccording to the method of producing a thermoplastic polyimide resinmentioned above, and then introducing a functional group such as anepoxy group, a vinyl group, an allyl group, a methacryl group, an acrylgroup, an alkoxysilyl group, a hydrosilyl group, a carboxy group, ahydroxy group or a cyano group into the polyimide by a chemicalreaction.

[0042] To the thermosetting resin may be further added a radicalreaction initiator such as organic peroxides; a reaction promotingagent; an auxiliary cross-linking agent such as triallyl cyanurate ortriallyl isocyanurate. And if necessary, commonly used epoxy curingagents such as acid dianhydride-, amine- and imidazole-based agents anda variety of coupling agents in order to improve heat resistance andadhesion property may be added. Further, for the purpose of controllingthe fluidity of the adhesive layer at the time of the thermal adhesion,a thermosetting resin may be added to the thermoplastic resin. To thisend, it is desired to add the thermosetting resin in an amount of 1 to10,000 parts by weight, preferably 5 to 2,000 parts by weight based on100 parts by weight of the thermoplastic resin. If the amount of thethermosetting resin is too large, the adhesive layer may become brittleand on the other hand, if the amount is too small, the fluidity of theresin of the adhesive layer may be deteriorated, burying of a circuitwithout voids may not be achieved or adhesion property may bedeteriorated.

[0043] One method for lamination by the adhesive is a method involvingsteps of laminating a metal foil on one or both faces of a syntheticresin film which is coated with an adhesive solution and dried, by usinga heating roll or a thermal press, and if necessary, further heating theresulting laminate to cure the adhesive. A special apparatus such as avacuum laminator or a vacuum press is also usable. For the heating tocure the adhesive, other than a common hot air oven, heating by farinfrared ray radiation, vacuum heating, microwave heating and othermanners can be employed and also heating by a thermal press inpressurized condition is also possible. Herein, the heating temperatureat the time of producing a laminate of the synthetic resin film and themetal foil is preferably at most 220° C., more preferably at most 200°C., and further preferably at most 180° C. If the heating temperature ishigher than 220° C., there is a tendency that a carrier film is notpeeled from the metal foil successfully. Also, in case of laminating thelaminate of the present invention on an inner layer wiring board, it ispreferable that the lamination is possible at a heating temperature ofat most 200° C. in order to utilize the laminate of the presentinvention for a wide range of purposes. Incidentally, it is preferablethat the heating temperature is as low as possible from many points ofview such as deflection of the laminate and peeling property of thecarrier-attached metal foil. In the meantime, since a synthetic resinfilm without adhesive has low heat resistance and an adhesive layer incase of using adhesive has low heat resistance it is preferable toadjust the temperature high to the extent that the heat resistance ofthe synthetic resin film and the adhesive is not deteriorated, dependingon each case.

[0044] As other methods of using an adhesive, it is possible to cast anadhesive resin solution on a support, remove the solvent to obtain asheet, and then laminate the sheet on the synthetic resin film. It isalso possible to laminate the adhesive on a metal foil and then laminatethe adhesive-attached metal foil on the synthetic resin film.

[0045] The thickness of the adhesive is preferably 1 to 15 μm afterdrying. If it exceeds 15 μm, that is, the insulating layer becomesthicker, it tends to become difficult to satisfy the requirement ofmaking the via diameter small along with the requirement of narrowingthe pitches. If it is thinner than 1 μm, a sufficient amount of theadhesive cannot be supplied to the roughened face of the metal foil andas a result, contact of the adhesive with the roughened surface of themetal foil is insufficient and therefore, the adhesion strength tends tobe decreased.

[0046] The polyimide film to be employed for the present invention canbe obtained by a well known method. That is, a poly(amide acid) polymersolution obtained by polymerizing a practically equivalent mole of oneor more tetracarboxylic acid dianhydride components and one or morediamine components in an organic polar solvent is spread and applied ona support member such as a glass plate or a stainless belt and thenthermally dried and cured to the extent that the resulting film has aself-supporting property. At that time, so-called chemical cure methodmay be carried out, which comprises adding, to the poly(amide acid), acuring agent (hereinafter, referred to as a chemical cure agent)produced by mixing dehydration agent for promoting imidization reactionof the poly(amide acid), a catalyst and a solvent before the poly(amideacid) polymer solution is spread and applied, then mixing and stirringthe mixture. As compared with a thermal cure method in which thepoly(amide acid) is imidized only by heating without using the chemicalcure agent, the chemical cure method is preferable in view of tensilemodulus of the polyimide film, adhesion strength to the thin film andother physical properties.

[0047] The typical tetracarboxylic acid dianhydride to be employed forproduction of the poly(amide acid) polymer includes aromatictetracarboxylic acid dianhydrides such as pyromellitic acid dianhydride,3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride,3,3′4,4′-diphenylsulfonetetracarboxylic acid dianhydride,1,4,5,8-naphthalenetetracarboxylic acid dianhydride,2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 4,4′-oxydiphthalicacid anhydride, 3,3′,4,4′-dimethyldiphenylsilanetetracarboxylic aciddianhydride, 3,3′,4,4′-tetraphenylsilanetetracarboxylic aciddianhydride, 1,2,3,4-furantetracarboxylic acid dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenyldipropane dianhydride,4,4′-hexafluoroisopropylidenediphthalic acid anhydride,3,3′,4,4′-biphenyltetracarboxylic acid dianhydride,2,3,3′,4′-biphenyltetracarboxylic acid dianhydride,p-phenylene-bis(trimellitic acid monoester anhydride) andp-phenylenediphthalic acid anhydride.

[0048] Among the tetracarboxylic acid dianhydrides, mixtures containing20 to 80% by mole of the pyromellitic acid dianhydride and an optionalratio of p-phenylenebis(trimellitic acid monoester anhydride) arepreferable to achieve tensile modulus of at least 4 GPa. However, thecombination of the tetracarboxylic acid dianhydrides described above isan example to obtain a polyimide film suitable for the synthetic resinfilm constituting the laminate of the present invention, and it is notlimited thereto. Thus, combinations and ratios of the tetracarboxylicacid dianhydrides to be employed may be changed to adjust properties ofthe polyimide film.

[0049] On the other hand, the typical diamine component to be employedfor production of the poly(amide acid) polymer includes aromaticdiamines such as 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,2,2-bis(4-aminophenoxyphenyl)propane, 1,4-bis(4-aminophenoxy)benzene,1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy) benzene,bis(4-(4-aminophenoxy)phenyl) sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, 4,4′-bis(4-aminophenoxy) biphenyl,2,2-bis(4-aminophenoxyphenyl)hexafluoropropane,4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone,9,9-bis(4-aminophenyl)fluorene, bisaminophenoxy ketone,4,4′-(1,4-phenylenebis(1-methylethylidene))bisaniline,4,4′-(1,3-phenylenebis(1-methylethylidene))bisaniline,m-phenylenediamine, p-phenylenediamine, 4,4′-diaminobenzanilide,3,3′-dimethyl-4,4′-diaminobiphenyl and3,3′-dimethoxy-4,4′-diaminobiphenyl, and other aliphatic diamines.

[0050] Among these diamine components, one example of a preferablecombination to obtain the polyimide film is a combination of 20 to 80%by mole of p-phenylenediamine and 80 to 20% by mole of4,4′-diaminodiphenyl ether. A more preferable combination is 30 to 70%by mole of the former and 70 to 30% by mole of the latter, and furtherpreferable combination is 40 to 60% by mole of the former and 60 to 40%by mole of the latter. Further, in place of p-phenylenediamine,4,4′-diaminobenzanilide may be employed. The combinations of the diaminecomponents described above are examples to obtain the polyimide filmsuitable for the synthetic resin film constituting the laminate of thepresent invention, and they are not limited thereto. Thus, combinationsand ratios of the diamine components to be employed may be changed tocontrol properties of the polyimide film.

[0051] Examples of organic polar solvents to be employed for thegeneration reaction of the poly(amide acid) copolymer include sulfoxidesolvents such as dimethyl sulfoxide and diethyl sulfoxide; formamidesolvents such as N,N-dimethylformamide and N,N-diethylformamide;acetamide solvents such as N,N-dimethylacetamide andN,N-diethylacetamide; pyrrolidone solvents such asN-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenol solvents suchas phenol, o-, m- or p-cresol, xylenol, halogenated phenol, catechol;hexamethyl phosphorus amide; γ-butyrolactone; and the like. They arepreferable to be employed alone or in form of mixtures and further, anaromatic hydrocarbon such as xylene or toluene may be used partially.

[0052] The weight average molecular weight of the poly(amide acid),which is a precursor of the polyimide film constituting a desirablelaminate of the present invention, is preferably 10,000 to 1,000,000. Ifthe weight average molecular weight is less than 10,000, the obtainedfilm tends to become brittle. On the other hand, if it exceeds1,000,000, the poly(amide acid) varnish, a polyimide precursor, has toohigh viscosity and handling may be difficult.

[0053] From the viewpoint of handling property, it is preferable that 5to 40% by weight, preferably 10 to 30% by weight of a poly(amide acid)copolymer is dissolved in the organic polar solvent.

[0054] A variety of organic additives, inorganic fillers or variousreinforcing materials may be added to the poly(amide acid) to obtain acomposite polyimide film.

[0055] The volatile component content and the imidization ratio of thegel film are controlled so as to keep them in prescribed ranges by athermal or chemical method, or combination of the thermal and thechemical method. From the viewpoint of properties of the obtainedpolyimide film and productivity, it is preferable to combine thechemical method and the thermal method together. More particularly, tothe poly(amide acid) copolymer solution is added a mixed solutioncontaining an aliphatic acid anhydride such as acetic anhydride in anamount about 0.5 to 10 times as much as the number by mole of thepoly(amide acid) portion of the poly(amide acid) copolymer solution, atertiary amine in an amount about 0.1 to 10 times as much and a solvent,followed by even mixing, and the resulting solution is spread on andapplied in the form of film, and heated at 50° C. to 200° C. for about 1minute to 1 hour to obtain the film.

[0056] The content of the volatile component of the obtained gel filmcan be calculated from the expression (1):

(A−B)×100/B   (1)

[0057] In the formula, the reference characters A and B represent thefollowings:

[0058] A: the weight of the gel film

[0059] B: the weight of the gel film after heating at 450° C. for 20minutes

[0060] The imidization ratio can be measured by an infrared absorptionspectrometry and calculated from the expression (2):

(C/D)×100/(E/F)  (2)

[0061] In the formula, the reference characteristics C, D, E and Frepresent the followings:

[0062] C: the absorption peak height of the gel film at 1,370 cm⁻¹

[0063] D: the absorption peak height of the gel film at 1,500 cm⁻¹

[0064] E: the absorption peak height of the polyimide film at 1370 cm⁻¹

[0065] F: the absorption peak height of the polyimide film at 1370 cm⁻¹

[0066] The content of the volatile component is in the range of 5 to300% by weight, preferably 5 to 100% by weight, and more preferably 5 to50% by weight. On the other hand, the imidization ratio is in the rangeof at least 50%, preferably at least 70%, more preferably 80% or higher,and most preferably at least 85%.

[0067] The synthetic resin film which constitutes the laminate of thepresent invention is preferably a polyimide film as described above. Inparticular, a polyimide film containing at least one element selectedfrom the group consisting of Al, Si, Ti, Mn, Fe, Co, Cu, Zn, Sn, Sb, Pb,Bi and Pd is used since it has excellent adhesion property. Thepolyimide film can be produced by immersing a partially imidized ordried poly(amide acid) film (hereinafter referred also as to a gel film)in a solution of a compound containing at least one element selectedfrom the group consisting of Al, Si, Ti, Mn, Fe, Co, Cu, Zn, Sn, Sb, Pb,Bi and Pd and then completely drying and imidizing the resulting gelfilm, or by applying the solution of the compound containing at leastone of the above elements to the gel film and then completely drying andimidizing the resulting gel film.

[0068] It is preferable that the gel film is immersed in a solution of acompound containing at least one of the above elements or applied withthe solution. As the compound containing at least one of the aboveelements, organic or inorganic compounds containing at least one of theabove elements is preferably used.

[0069] To say more particularly, the inorganic compounds include, forexample, halogenides such as chlorides and bromides, oxides, hydroxides,carbonates, nitrates, nitrites, phosphates, sulfates, silicates,borates, condensed phosphates and the like.

[0070] The organic compounds include, for example, those containingneutral molecules such as alkoxides, acylates, chelates, diamines anddiphosphines; those containing acetylacetonate ion, carboxylic acid ionor dithiocarbamic acid ion; and also cyclic legands such as porphyrin.

[0071] The concentration of the solution is preferably 0.01 to 10% byweight, more preferably 0.1 to 5% by weight.

[0072] Preferable elements in the compound having at least one of theabove elements, in which the gel film is immersed or which is applied tothe gel film, are Si and Ti. The compound containing these elements,such as a silicon compound or a titanium compound, may be supplied inform of alkoxide, acylate, chelate or metal salt.

[0073] The silicon compound includes aminosilane-based compounds such asN-β-(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane;and epoxysilane-based compounds such asβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldimethoxysilane. Preferable titanium compoundsare those represented by the following general formula. To say moreparticularly, examples thereof include tri-n-butoxytitaniummonostearate, diisopropoxytitanium bis(triethanolaminate), butyltitanatedimer, tetra-n-butyltitanate, tetra(2-ethylhexyl)titanate, titaniumoctylene glycolate and the like. In addition, dihydroxy-bis(ammoniumlactate) titanium, dihydroxytitanium bislactate and the like are alsousable. The most preferable one is tri-n-butoxytitanium monostearate ordihydroxytitanium bislactate.

(R¹O)_(m)—Ti—(OX)_(4−m)

[0074] wherein m=an integer of 0 to 4;

[0075] a hydrocarbon group having 3 to 18 carbon atoms, or a carboxylicacid having 3 to 18 carbon atoms and ammonium salt thereof;

[0076] R¹: H or a hydrocarbon group having 3 to 18 carbon atoms;

[0077] R² and R³: a hydrocarbon group having 3 to 18 carbon atoms;

[0078] R⁴: a hydrocarbon group having 3 to 18 carbon atoms or

[0079] R⁵ and R⁶: a hydrocarbon group having 3 to 18 carbon atoms; and

[0080] R⁷: a hydrocarbon group having 2 to 18 carbon atoms.

[0081] The solvent to be employed for the solution may be any solventwhich can dissolve the compound. For example, water, toluene,tetrahydrofuran, 2-propanol, 1-butanol, ethyl acetate,N,N-dimethylformamide, acetylacetone and the like are usable. Thesesolvents may be used in form of a mixture of two or more. In the presentinvention, N,N-dimethylformamide, 1-butanol, 2-propanol, and water areespecially preferable.

[0082] After applying the solution to the gel film or immersing the gelfilm in the solution, it is preferable to add a step of removing excessdroplets on the surface because such a step enables to obtain apolyimide film excellent in appearance and free from surface unevenness.To remove the droplets, a known method using a nip roll, an air knife, adoctor blade and the like can be employed, and the nip roll ispreferably used from the viewpoint of appearance, droplet removal andworkability of the film.

[0083] The gel film after being applied with the solution or beingimmersed in the solution is held at its edges by using tenter clips orpins for shrinkage inhibition, in order to prevent the film fromshrinking in the tentering step, and then heated step by step, dried andimidized to obtain the polyimide film. To say more particularly, thefilm is preferably heated step by step from about 200° C. and finally at500° C. or higher for 15 to 600 seconds.

[0084] The synthetic resin film made of the polyimide film obtained insuch a manner is provided with hydrolysis resistance. That is, the filmhas a characteristic such that the retention ratio of the tearpropagation strength is at least 80% after exposure to environmentalconditions of 150° C. and 100% RH for 12 hours compared with the tearpropagation strength before the exposure.

[0085] The laminate produced by laminating the polyimide film with ametal layer has a high initial adhesion strength between the metal layerand the film, and shows sufficient heat resistance and heat-and-humidityresistance of the adhesion. When the film is employed for the laminateof the present invention or a multilayer wiring plate, the obtainedproduct is excellent in electric insulation property without causinginsulation deterioration in high temperature and high humidityenvironments.

[0086] The thickness of the polyimide film is not particularly limited,but in order to meet the requirement of high capability of electricappliances, the thinner the film the more preferable. To say moreparticularly, suitable films are those having a thickness of at most 50μm, preferably at most 25 μm, and more preferably at most 15 μm. Thereis no particular lower limit of the thickness of the polyimide film, butthe lower limit of the film thickness is about 1 μm in the presenttechnical level from the viewpoint that it is possible to form a filmwith practically allowable evenness and practically usable strength.

[0087] The tensile modulus of the polyimide film is preferably at least4 GPa, more preferably at least 6 GPa. If it is lower than 4 GPa,handling of the film becomes difficult, and wrinkling tends to be causedeasily when the film is laminated on a thin copper foil. On the otherhand, the upper limit is not particularly limited. In general, however,the higher the elastic modulus, the more brittle the film. Therefore, itis preferable to adjust the elastic modulus to such a value thatbrittleness is not significant.

[0088] The linear expansion coefficient of the polyimide film ispreferably at most 20 ppm, more preferably at most 13 ppm. Since thelaminate of the present invention has a layered structure with a metal,if the linear expansion coefficient of the polyimide film isconsiderably different from that of the metal, deflection tends toincrease or the dimensional accuracy tends to be deteriorated. Takingsuch a matter into consideration, the upper limit and the lower limit ofthe linear expansion coefficient are 20 ppm and 0 ppm, respectively.

[0089] The polyimide film of the present invention may be incorporatedwith an inorganic or organic filler, a plasticizer such as organicphosphorus compound or an oxidation inhibitor in a known manner. Inaddition, for the purpose of improving the adhesion property between themetal layer and the adhesive layer, the film may be subjected to heatingtreatment, sand blast treatment, degreasing washing treatment,ultraviolet radiation treatment, flaming treatment and the like. Thetreatment may be carried out by employing known surface treatmentmethods separately or in combination of some of the treatment methodsincluding a method for applying a variety of organic substances such asa thermosetting resin, a thermoplastic resin, an organic monomer or acoupling agent as a primer; a method for surface treating with a metalhydroxide or an organic alkali; a method for grafting the surface,corona discharge treatment; and plasma discharge treatment.

[0090] The method for laminating the metal layer on the polyimide filmcontaining at least one element selected from the group consisting ofAl, Si, Ti, Mn, Fe, Co, Cu, Zn, Sn, Sb, Pb, Bi and Pd may be selectedfrom the group consisting of sputtering, ion plating, electron beamevaporation, resistance heating evaporation, chemical plating andelectric plating from the viewpoint that the methods provide excellentadhesion property. These methods may be carried out in a common manner,and metals such as copper, nickel, tin, solder and chromium areemployed. The physical evaporation methods such as sputtering, ionplating, electron beam evaporation and resistance heating evaporationare not industrially suitable to form a metal film of several μm thick.Therefore, after a thin film with a thickness of at most 1 μm is formedby the physical evaporation methods, it is preferable to successivelycarry out chemical plating or electric plating to give a desiredthickness.

[0091] The metal foil with a thickness of 5 μm or thinner tends to havelow strength, low stiffness and inferior handling property. In thepresent invention, it is preferable to improve the handling property byusing a metal foil thinner than 10 μm together with a carrier havingcertain stiffness. In this case, the carrier is composed of a metalfoil, a metal plate or a polymer film. It is preferable that the carrieris laminated on the metal foil according to a sticking method or abonding method with such a peeling strength that the carrier can bepeeled relatively easily by a weak force when it becomes unnecessary.The peeling strength is preferably lower than 200 gf/cm. In this case,it is preferable that the carrier is laminated with the metal foil atthe time of handling the metal foil, but at the time of removing thecarrier after laminating the metal foil with the polyimide film, it ispreferable that the carrier is peeled smoothly from the metal foil.Accordingly, it is preferable that the metal foil has an adhesionstrength as high as preventing the carrier from peeling at the time ofhandling the metal foil and lower than the adhesion strength between themetal foil and the polyimide film.

[0092] The metal foil is subjected to various steps and receives stressof heat, pressure or tensile force when laminated with the polyimidefilm. It is desired that the carrier and the metal foil have similardimensional changes which are caused by these stresses. For thesereasons, a metal similar to the foil is the most preferable as thematerial of the carrier for the metal foil.

[0093] The proper thickness of the carrier for the metal foil differsdepending on the material. However, in many cases, the thickness ispreferably 10 to 300 μm. If the thickness of the carrier exceeds 300 μm,the handling property is adversely deteriorated or the cost tends to beincreased. On the other hand, if it is thinner than 10 μm, it tends tobe difficult to improve the handling property, which is the originalpurpose of the carrier.

[0094] Furthermore, in the present invention, the metal foil may besubjected to a mat treatment for roughening one or both faces or ablackening treatment for forming an oxidation layer in order to improvethe adhesion property of the metal foil to the synthetic resin film andthe adhesive. In addition, in order to improve the heat resistance andthe humidify resistance of the metal foil, one or both faces of themetal foil may be subjected to rust prevention treatment and glossingtreatment.

[0095] A protection film may also be disposed on the surface of thelaminate of the present invention in order to protect the surface of thelaminate.

[0096] The laminate of the present invention obtained in the manner asdescribed above comprises a synthetic resin film having excellentappearance without surface unevenness as an insulating layer and a thinmetal layer. Accordingly, it is useful for narrowing the pitches ofcircuits. Further, a printed wiring board manufactured by using thelaminate has excellent adhesion property between its metal layer andsynthetic resin film, and therefore adhesion to the synthetic resin filmis excellent even if the circuit is narrowly pitched. Also, the printedwiring board shows excellent characteristics such that the adhesionbetween the synthetic resin film and the patterned circuit is stableagainst factors such as heat and humidity. Accordingly, the laminate ofthe present invention has high heat resistance, wiring patterns withnarrow pitches, vias with a small diameter, insulating layer havinguniform thickness, and stable adhesion between the metal layer and thesynthetic resin film, and is suitably used for a printed wiringsubstrate and a multilayer printed wiring board contributing tominiaturization, high capability and functional improvement ofelectronic equipment.

[0097] Although the laminate of the present invention and itsconstituent materials are described above, the present invention is notlimited to these exemplified materials. The present invention can becarried out in embodiments of various improvement, modification oralteration based on the knowledge of persons skilled in the art withinthe scope of the present invention.

[0098] Hereinafter, the present invention will be described withreference to Examples. In Examples, ODA represents 4,4′-diaminodiphenylether; p-PDA represents p-phenylenediamine; BAPS-M representsbis(4-(3-aminophenoxy)phenyl)sulfone; DABA represents4,4′-diaminobenzanilide; PMDA represents pyromellitic acid dianhydride;TMHQ represents p-phenylene bis(trimellitic acid monoester anhydride);ESDA represents 2,2-bis(4-hydroxyphenyl)propanebenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride; and DMFrepresents N,N-dimethylformamide. The tensile modulus of the syntheticresin film was measured in accordance with the method of ASTM D 882.

EXAMPLE 1

[0099] (1) A separable flask was charged with DMF, 1 equivalent of p-PDAand 1 equivalent of ODA. The mixture was sufficiently stirred at a roomtemperature until the diamine compounds were completely dissolved, andthen cooled with ice. Subsequently, 1 equivalent of TMHQ was addedthereto and stirring was carried out for 40 minutes with cooling. Then,1 equivalent of PMDA was dissolved in DMF and this was gradually addedto the mixture. Thereafter, stirring was carried out for 1 hour withcooling to obtain a DMF solution of a poly(amide acid) having a weightaverage molecular weight of about 100,000. The amount of DMF wascontrolled so that the concentration of monomers of the diamino compoundand the aromatic tetracarboxylic acid compound was 18% by weight.

[0100] To 100 g of the poly(amide acid) solution were added 10 g ofacetic acid anhydride and 10 g of isoquinoline. The resulting mixturewas stirred until homogeneous and defoaming was carried out. Theresulting solution was spread and applied on a glass plate, and dried atabout 110° C. for about 5 minutes. Thereafter, the poly(amide acid) filmwas peeled from the glass plate to obtain a gel film which contains 40%by weight of a volatile component and has a imidization ratio of 85% andself-supporting property. The gel film was immersed in adihydroxytitanium bislactate/1-butanol solution having a titaniumconcentration of 400 ppm for 10 seconds and excess droplets wereremoved. The gel film was further fixed in a frame and then heated atabout 200° C. for about 10 minutes, at about 300° C. for about 10minutes, at about 400° C. for about 10 minutes and at about 500° C. forabout 10 minutes to carry out dehydration ring closing and drying toobtain a polyimide film with a thickness of about 12 μm. The obtainedpolyimide film had a tensile modulus of 6 GPa and a linear expansioncoefficient of 12 ppm.

[0101] (2) A separable flask was charged with DMF and 1 equivalent ofBAPS-M. The mixture was sufficiently stirred at a room temperature untilBAPS-M was completely dissolved and then cooled with ice. Subsequently,1 equivalent of ESDA was added thereto and stirring was carried out for1 hour with cooling to obtain a DMF solution of a poly(amide acid). Theamount of DMF was controlled so that the concentration of monomers ofthe diamino compound and the aromatic tetracarboxylic acid compound was30% by weight. To 500 g of the poly(amide acid) solution were added 35 gof β-picoline and 60 g of acetic acid anhydride, and stirring wascarried out for 1 hour. Thereafter, further stirring was carried out for1 hour at 100° C. to promote imidization. Subsequently, the resultingsolution was added to methanol stirred at a high speed drop by drop toobtain a polyimide resin in the form of filaments. The resin was driedat 100° C. for 30 minutes and pulverized by a mixer, and the resultantwas washed with methanol using a Soxhlet's extractor and dried at 100°C. for 2 hours to obtain a polyimide powder.

[0102] (3) Twenty g of the polyimide powder obtained in (2), 5 g ofEpicoat 828 (available from Yuka Shell Epoxy K.K.) as a bisphenol Aepoxy resin and 0.015 g of 2-ethyl-4-methylimidazole as a curing agentwere dissolved in 83 g of DMF.

[0103] (4) The varnish obtained in (3) was spread and applied on bothfaces of the polyimide film obtained in (1) so that the thickness of therespective films became 5 μm after drying. The applied varnish was thendried at 100° C. for 10 minute and at about 150° C. for about 20 minutesto obtain a laminate with a total thickness of 22 μm. A 3-μm thickcopper foil with a 35-μm thick carrier copper foil was pressed on oneface of the obtained laminate at 200° C. under 3 MPa for 5 minutes tolaminate the copper foil with the polyimide film. The adhesive on bothfaces of the synthetic resin was half-cured at this stage.

[0104] (5) The laminate obtained in (4) was laminated on the surface ofa printed wiring board having wiring patterns thereon in such a mannerthat the adhesive and the wiring patterns were brought into contact witheach other. The resulting laminate was preliminarily bonded by pressingthe same at 200° C. under 3 MPa for 5 minutes. Thereafter, the resultinglaminate was heated at 170° C. for 3 hours in a hot air oven to cure theadhesive completely, and then the carrier of the copper foil was peeledto obtain a multilayer printed wiring board having a 3-μm thick metallayer on the surface.

[0105] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection or pattern exfoliation.

EXAMPLE 2

[0106] A multilayer printed wiring board having a 3-μm thick metal layeron the surface was obtained in the same manner as in Example 1, exceptthat a dihydroxytitanium bislactate/1-butanol solution having a titaniumconcentration of 1,000 ppm was used.

[0107] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection or pattern exfoliation.

EXAMPLE 3

[0108] A multilayer printed wiring board having a 3-μm thick metal layeron the surface was obtained in the same manner as in Example 1, exceptthat a γ-aminopropyltriethoxysilane/1-butanol solution having a siliconconcentration of 400 ppm was used.

[0109] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection or pattern exfoliation.

EXAMPLE 4

[0110] A multilayer printed wiring board having a 3-μm thick metal layeron the surface was obtained in the same manner as in Example 1, exceptthat a γ-aminopropyltriethoxysilane/water solution having a siliconconcentration of 3,000 ppm was used.

[0111] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection or pattern exfoliation.

EXAMPLE 5

[0112] A separable flask was charged with DMF, 3 equivalents of DABA and1 equivalent of ODA. The mixture was sufficiently stirred at roomtemperature until the diamine compounds were completely dissolved andthen cooled with ice. Subsequently, 4 equivalents of TMHQ was added andstirred with cooling for 1 hour to obtain a DMF solution of a poly(amideacid) having a weight average molecular weight of about 100,000. Theamount of DMF was controlled so that the concentration of monomers ofthe diamino compound and the aromatic tetracarboxylic acid compound was18% by weight.

[0113] To 100 g of the poly(amide acid) solution were added 10 g ofacetic acid anhydride and 8 g of isoquinoline. The resulting mixture wasstirred until homogeneous and defoaming was carried out. The resultingsolution was spread and applied on a glass plate, and dried at about110° C. for about 5 minutes. Thereafter, the poly(amide acid) film waspeeled from the glass plate to obtain a gel film which contains 40% byweight of a volatile component and has a imidization ratio of 85% andself-supporting property. The gel film was immersed in adihydroxytitanium bislactate/1-butanol solution having a titaniumconcentration of 1,000 ppm for 10 seconds and excess droplets wereremoved. The gel film was further fixed in a frame and then heated atabout 200° C. for about 10 minutes, at about 300° C. for about 10minutes, at about 400° C. for about 10 minutes and at about 500° C. forabout 10 minutes to carry out dehydration ring closing and drying toobtain a polyimide film with a thickness of about 12 μm. The obtainedpolyimide film had a tensile modulus of 10 GPa and a linear expansioncoefficient of 5 ppm.

[0114] A multilayer printed wiring board having a 3-μm thick metal layeron the surface was obtained in the same manner as in Example 1, exceptthat the above polyimide film was used.

[0115] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection or pattern exfoliation.

EXAMPLE 6

[0116] A multilayer printed wiring board having a 3-μm thick metal layeron the surface was obtained in the same manner as in Example 5, exceptthat a γ-aminopropyltriethoxysilane/water solution having a siliconconcentration of 3,000 ppm was used.

[0117] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection, or pattern exfoliation.

EXAMPLE 7

[0118] (1) A 20-nm thick nickel layer and successively a 100-nm thickcopper layer were formed by magnetron DC sputtering method on thepolyimide film produced in (1) of Example 1. Subsequently, a copperlayer was formed by an electroplating method using a copper sulfateplating solution to give a total thickness 3 μm. The aboveelectro-copper plating was carried out by plating at room temperaturefor 6 minutes after preliminary washing for 30 seconds in a 10% sulfuricacid solution. The current density in that case was 2 A/dm².

[0119] (2) Subsequently, the varnish obtained in (3) of Example 1 wasspread and applied on the polyimide film face of the copper thinfilm-bearing polyimide film obtained in (1) so that the thickness was 9μm after drying. The applied varnish was then dried at 100° C. for 10minute and at about 150° C. for about 20 minutes to obtain a laminate.

[0120] (3) In the same manner as described in (5) of Example 1, thelaminate obtained in (2) was laminated on the surface of a printedwiring board having wiring patterns to obtain a multilayer printedwiring board bearing a 3 μm-thick metal layer on the surface. The copperfoil on the surface of the obtained multilayer printed wiring board waspatterned by using an etching resist of a photosensitive resin to formcircuits with lines and spaces of 25 μm and 25 μm. The circuitpatterning was excellently carried out without causing short-circuit,disconnection or pattern exfoliation.

EXAMPLE 8

[0121] A multilayer printed wiring board having a 3-μm thick metal layeron the surface was obtained in the same manner as in Example 7, exceptthat the polyimide film produced in Example 5 was used.

[0122] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. The circuit patterning was excellently carried out withoutcausing short-circuit, disconnection or pattern exfoliation.

COMPARATIVE EXAMPLE 1

[0123] A multilayer printed wiring board having a 9-μm thick metal layeron the surface was obtained in the same manner as in Example 1, exceptfor using a 9-μm thick electrolytic copper foil instead of the 3-μmthick foil. The copper foil on the surface of the obtained multilayerprinted wiring board was patterned by using an etching resist of aphotosensitive resin, and it was tried to form circuits with lines andspaces of 25 μm and 25 μm. However, the line width was not uniform andshort-circuit and disconnection took place.

COMPARATIVE EXAMPLE 2

[0124] A multilayer printed wiring board was obtained in the same manneras in Example 1, except that a series of the steps of immersing a gelfilm in the dihydroxytitanium bislactate/1-butanol solution having atitanium concentration of 400 ppm for 10 seconds and removing excessdroplets.

[0125] The copper foil on the surface of the obtained multilayer printedwiring board was patterned by using an etching resist of aphotosensitive resin to form circuits with lines and spaces of 25 μm and25 μm. However the adhesion strength between the circuit layer and thesynthetic resin film layer was weak and accordingly, the patternexfoliation took place.

Industrial Applicability

[0126] The laminate of the present invention can provide a multilayerprinted wiring board which have high heat resistance, wiring patternswith narrow pitches, vias with a small diameter, insulating layer havinguniform thickness and stable adhesion between conductors. Also, thelaminate of the present invention can be used for production of amultilayer wiring board in various manners.

1. A laminate comprising a metal layer laminated on one or both faces ofa synthetic resin film, wherein the metal layer is a metal foil having athickness of at most 5 μm.
 2. The laminate of claim 1, wherein the metallayer is laminated on one face of the synthetic resin film and anadhesive layer is laminated on the other face of the synthetic resinfilm.
 3. The laminate of claim 1 or 2, wherein the synthetic resin filmand the metal layer are bonded with an adhesive.
 4. The laminate ofclaims 2 or 3, wherein the adhesive contains a polyimide resin.
 5. Thelaminate of claim 4, wherein the adhesive containing the polyimide resincontains a thermosetting resin.
 6. The laminate of claim 2, 3, 4 or 5,wherein the adhesive is laminated on a metal layer or a circuitsubstrate at a temperature of at most 220° C.
 7. The laminate of claim1, wherein a polyimide film is used as the synthetic resin film.
 8. Thelaminate of claim 7, wherein the polyimide film has a thickness of atmost 50 μtm, a tensile modulus of at least 4 GPa and a coefficient oflinear expansion of at most 20 ppm.
 9. The laminate of claim 1, whereinthe metal foil is a metal foil supported by a carrier.
 10. The laminateof claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 , wherein the synthetic resin filmis a polyimide film obtained by immersing a partially imidized orpartially dried poly(amide acid) film in a solution of a compoundcontaining at least one element selected from the group consisting ofaluminum, silicon, titanium, manganese, iron, cobalt, copper, zinc, tin,antimony, lead, bismuth and palladium or by applying the solution to thefilm, and then completely drying and imidizing the poly(amide acid)film, the resulting polyimide film containing at least one of theelements.
 11. A laminate comprising a metal layer having a thickness ofat most 5 μm on one or both faces of a synthetic resin film, wherein thesynthetic resin film is a polyimide film obtained by immersing apartially imidized or partially dried poly(amide acid) film in asolution of a compound containing at least one element selected from thegroup consisting of aluminum, silicon, titanium, manganese, iron,cobalt, copper, zinc, tin, antimony, lead, bismuth and palladium or byapplying the solution to the film, and then completely drying andimidizing the poly(amide acid) film, the resulting polyimide filmcontaining at least one of the elements.
 12. The laminate of claim 11,wherein the metal layer having a thickness of at most 5 μm is laminatedon one face of the synthetic resin film and an adhesive layer islaminated on the other face of the synthetic resin film.
 13. Thelaminate of claim 12, wherein the adhesive contains a polyimide resin.14. The laminate of claim 13, wherein the adhesive contains athermosetting resin.
 15. The laminate of claim 13 or 14, wherein theadhesive is laminated on a metal layer or a circuit substrate at atemperature of at most 220° C.
 16. The laminate of claim 11, 12, 13, 14or 15, wherein the metal layer is formed directly on the synthetic resinfilm by a method selected from the group consisting of sputtering, ionplating, electron beam evaporation, resistance heating evaporation,chemical plating, and electroplating.